Surface charge is the electric charge present at an interface. There are many different processes which can lead to a surface being charged, including adsorption of ions, protonation/deprotonation, and the application of an external electric field. Surface charge causes a particle to emit an electric field, which causes particle repulsions and attractions, and is responsible for many colloidal properties.
Surface charge practically always appears on an object surface when it is placed into a fluid. All fluids contain ions, positive (cations) and negative (anions). These ions interact with the object surface. This interaction might lead to the adsorption of some of them on the surface. If the number of adsorbed cations exceeds the number of adsorbed anions, the surface would gain total positive electric charge.
There is another possible mechanism leading to surface charging. It is dissociation of the surface chemical group.
Read more about Surface Charge: Surface Charge Density, Interfacial Potential, Applications of Surface Charge
Famous quotes containing the words surface and/or charge:
“I cannot but conclude the bulk of your natives to be the most pernicious race of little, odious vermin that Nature ever suffered to crawl upon the surface of the earth.”
—Jonathan Swift (1667–1745)
“It is hereby earnestly proposed that the USA would be much better off if that big, sprawling, incoherent, shapeless, slobbering civic idiot in the family of American communities, the City of Los Angeles, could be declared incompetent and placed in charge of a guardian like any individual mental defective.”
—Westbrook Pegler (1894–1969)